Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from finance leases	$ 7,657
Operating cash flows from operating leases	186,868
Financing cash flows from finance leases	$ 2,941	$ 0